Vapor generator wall construction



1967 K. FRANZMANN VAPOR GENERATOR WALL CONSTRUCTION 2 Sheets-Sheet 1Filed May 5, 1965 Y m R O z m T n N a R E r 0 W T .T 2 H .A a 2 9 1 2 HK 2 oooooomvdooooooooo F G Y F. w /0 B Jan. 24, 1967 K. FRANZMANN3,299,858

VAPOR GENERATOR WALL CONSTRUCTION Filed May 5, 1965 2 Sheets-Sheet 2United States Patent VAPOR GENERATOR WALL CONSTRUCTION Karl Franzmann,Oberhausen, Rhineland, Germany, as-

signor to Babcock & Wilcox, Limited, London, England, a corporation ofGreat Britain Filed May 5, 1965, Ser. No. 453,371 11 Claims. (Cl. 122-6)This invention relates generally to tubular fluid heat ing units andmore particularly to a steam generator having a furnace or radiationchamber which is bounded by a wall formed with parallel contiguousfluid-cooled tubes, rigidly united along their lengths to form agas-tight wall panel.

In a modern high capacity steam generator, there is a considerablepressure differential between the furnace or combustion chamber and theoutside atmosphere. Where, as in the usual installation, the combustionair is pressurized sufiiciently to overcome the total fire-side draftloss of the unit, the combustion chamber or furnace will be operating ata substantial positive pressure. On the other hand, when gases are drawnthrough the unit, as by an induced draft fan, the furnace may beoperating under negative pressure. In either instance, there normallyresults a considerable pressure differential across the boundary wallsof the furnace. To prevent leakage of air or combustion gases into orout of the furnace, various types of gas-tight furnace wall casings havebeen developed and used; however, such casings have proven diflic'ult todesign because of the many openings required to accommodate the passageof wall tubes, supply, discharge and mixing tubes through the casing.Accordingly, it. has become common practice to construct the furnacechamber of fluid-cooled boundary walls comprising a plurality ofparallel, contiguous tubes rigidly interconnected, as by welding, alongtheir lengths so as to form gas-tight wall panels.

Rigid panel walls of this type can be utilized in a zone of intenseradiant heat emission only if the temperature of the fluid flowingthrough the plurality of tubes in each panel is substantially the sameand the heat absorption rate across the width of the panel issubstantially uniform. If these conditions are not met, severe thermalstresses may be induced in the wall panels. Moreover, the condition ofsubstantially equal fluid temperature in all the tubes of a panel canmost easily be achieved if the fluid flowing through the tubes ismaintained at a level no higher than the saturation temperaturecorresponding to the fluid pressure within the tubes. It would thereforebe desirable to construct the panel walls of the furnace chamber ofevaporator or steam generator tubes only; however, this becomesincreasingly diflicult as the operating pressure is increased because ofthe corresponding decrease in the heat of vaporization in thesubcritical pressure range. Thus it is difficult to design the furnacechamber. walls of a high capacity, high pressure vapor generator so thatall of the wall tubes exposed to the high radiating temperatures of thefurnace chamber handle fluid at temperatures no higher than thesaturation temperature corresponding to operating pressure.

So that the fluid in the tubes of the panel walls will not exceedsaturation temperature, it is proposed according to the presentinvention, that the usual design of panel wall (tubes on centers equalto or less than about 1.5 times their outside diameter) be used in thoseportions of the furnace wall exposed to relatively low levels of radiantheat emission, and that the spacing between tubes in the portions of thefurnace wall exposed to relatively intense radiant heat emission bespaced more widely (so that the center-to-center distance betweenadjacent tubes is about 4.5 times their diameter). Further, it isproposed that this latter (high radiation) portion of the furnace wallbe protected from intense radiation by a shielding or anti-radiationwall formed of shielding tubes disposed on the gas side of the wallpanel adjacent the more widely spaced tubes. The spacing of theshielding tubes should advantageously be closer than the spacing of theadjacent protected portion of the panel wall tubes to produce thedesired radiation shielding effect. Moreover, in order that theradiation passing between the tubes of the anti-radiation wall does notproject onto individual components of the panel wall, it is proposedthat the shielding tubes be oriented so that their longitudinal axes areat intersecting angles with the longitudinal axes of the adjacent panelwall tubes, preferably at substantially right angles.

The anti-radiation tube wall shoulld be space-d sufliciently from theprotected panel wall so that slag accumulations will not tend to form inthe space between the adjacent walls, or so that if such accumulationsdo form therein, they can be easily removed by conventional means suchas soot blowers. The anti-radiation wall may be secured in spacedrelation to and supported by the shielded panel wall by means ofsuitable connectors, which are preferably attached directly by weldingto the center of the intertube portion of the shielded panel wall sothat heat absorbed by each connector is distributed as evenly aspossible between the adjacent panel wall tubes.

So that the evaporating heating surface may be conserved foradvantageous use in the panel boundary walls of the steam generator, itis contemplated that the shieldin g tubes of the anti-radiation wallwill be vapor-cooled heating surfaces.

More specifically, according to the present invention, there iscontemplated for use in a forced-circulation steam generator, a wallconstruction wherein first straight panel wall tubes are connectedbetween a supply header and a collection header, and second panel walltubes, having U- shaped legs disposed in the plane of the first panelwall tubes, are connected for serial flow with respect to the firstpanel wall .tubes between the collection header and an outlet header,the U-shaped bends of the second pan-- el wall tubes being in a zone ofthe panel wall shielded by the anti-radiation tube wall.

The various features of novelty which characterize the invention arepointed out with particularity in the claims annexed to and forming apart of this specification.

For a better understanding of the invention, its operating advantagesand specific objects attained by its use, refer-- ence should be had tothe accompanying drawings and descriptive matter in which there isillustrated and described a preferred embodiment of the invention.

FIG. 3 is a sectional view taken along line 3 -3 of;

FIG. 1;

FIG. 4 is a sectional view taken along line 4- 4 of FIG. 3;

FIG. 5 is a sectional view taken along line 55 of FIG. 4; and

FIG. 6 is a diagrammatic side view of a vapor generator showing apossible location on the wall construction of FIGS. 1 through 5.

As shown in the drawings, the tubular panel wall 10 includes an inletheader 11 and a parallel collection headerv 12, which headers areinterconnected by a plurality of upwardly extending spaced, parallelwall tubes 13 forthe flow of coolant fluid upwardly therethrough. In

t the lower portion of the panel wall 10, adjacent tubes are rigidlyinterconnected, as by Welding, by plate means such as relatively widefins or web members 14 positioned in the spaces between the tubes so asto render the panel wall gas-tight, the Weld preferably being on theside of the panel wall 10 that is not exposed to the radiant heat of thefurnace chamber 9. g

In the upper portion of the panel wall 10, disposed between the panelwall tubes 13 are U-shaped tubes having upwardly extending legs 16 and17 connected in pairs at their lower ends by U-bend sections 19, theupper ends of the tube legs 16 and 17 being respectively connected tothe collection header 12 and an outlet header which is disposed parallelto and slightly above and to the rear of collection header 12. Panelwall tubes '13 and the tube legs 16 and 17 are preferably of the samediameter, so that when constructed in the form of a planar wall, auniform panel of the usual type is presented.

By arranging the tubes 13 on centers of about 4.5 times their diameter,the interposition of the tube legs 16 and 17 will result in the upperportion of the panel wall 10 having tubes spaced on centers equal toabout 1.5 times their diameter. The intert-ube spaces in the upperportion of the panel wall 10 are suitably closed to render the panelwall gas-tight by welding to the tubes along their lengths relativelynarrow fin or web members 18. In the vicinity of the U-bend sections 19,the web members 14 may be connected as necessary to the Web members 18so as to preserve the gas-tight integrity on the wall 10.

From the above, it can be seen that the fluid to be heated flows throughthe panel wall 10 as follows: fluid enters via the inlet or supplyheader 11, then flows upwardly in parallel flow relationship through thepanel wall tubes 13 to the collection header 12 from whence it flowdownwardly through tube legs 16, around the U- bend sections 19 andupwardly through tube legs 17 to the outlet header 20. It iscontemplated, according to the present invention, that the fluid thusflowing through the panel Wall 10 will preferably not attain atemperature higher than the saturation temperature corresponding to thepressure within the pressure parts of the panel wall 10, and that thefluid will be passed from the outlet header 20 to some additional heatexchange means wherein the fluid temperature will eventually beincreased into the superheat range.

Disposed on the gas side of and spaced from the panel wall 10 is ananti-radiation wall 22 comprising a plurality of horizontal, spaced,parallel shielding tubes 21, which tubes are preferably installed incoplanar fashion with relatively close spacing therebetween (tubecenters of about 1.1 to 1.2 times the tube diameter) so as toeffectively shield the wall tubes 13 from a major portion of theradiation from the furnace chamber 9. Fluid, preferably in the form ofvapor, is passed through the shielding tubes 21 either serially or inparallel flow relation. It should be recognized that the interpositionof the antiradiation wall 22 between the high radiant energy source(furnace chamber 9) and the panel wall 10, will materially reduce thetotal radiant heat absorption in the shielded area of the panel wall 10.

The shielding tubes 21 are attached to and supported by the panel wall10 in spaced relation thereto by suitable connectors, which connectorsmay include vertical support plates 24 welded to the lateral centers ofthe web members 14 at spaced locations across the width of panel wall10. The support plates 24 are formed with openings 25 arranged to acceptU-shaped lugs 23 which are welded to the shielding tubes 21 on the sidesthereof not exposed to the direct radiation of the furnace chamber 9.

Referring to FIG. 6, the above-described wall construction is preferablyembodied in a vapor generator having boundary walls (including wall 10)defining furnace chamber 9 in confining high temperature radiant heatinggases produced, for example, by burner means 29. Fluid flows from thevapor generating tubes of the furnace boundary walls to a superheater 28and thence through the tubes 21 of the shielding wall 22.

While in accordance with the provisions of the statutes there isillustrated and described herein a specific embodiment of the invention,those skilled in the art will understand that changes may be made in theform of the invention covered by the claims, and that certain featuresof the invention may sometimes be used to advantage without acorresponding use of the other features.

What is claimed is:

1. In a fluid heating unit, upright boundary w'alls forming a heatingchamber confining high temperature radiant heating gases, one of saidupright boundary walls including a plurality of parallel contiguousvapor generating tubes rigidly united along their lengths'to form arigid gas-tight Wall panel, means for passing fluid in parallel flowrelation through said tubes at a temperature substantially equal to thesaturation temperature corresponding to the pressure of the fluid withinsaid tubes, and means for shielding a substantial portion of said oneboundary wall from radiation within said furnace chamber including ashielding wall disposed on the gas side of said boundary wall andcomprising a plurality ofshielding tubes arranged in side-by-siderelation, and means for passing fluid through said shielding tubes.

2. In a high pressure fluid heating unit, upright boundary walls forminga heating chamber confining high temperature radiant heating gases, oneof said upright boundary walls including a plurality of parallelcontiguous vapor generating tubes rigidly united along their lengths toform a rigid gas-tight wall panel, means for passing a fluid in parallelflow relation through said tubes at a temperature substantially equal tothe saturation temperature corresponding to the pressure of the fluidwithin said.

tubes, and means for shielding a substantial portion of said oneboundary wall from radiation within said furnace chamber including ashielding wall disposed on the gas side of said boundary wall andcomprising a plurality'of shielding tubes arranged in side-by-siderelation, and

lel flow relation through said tubes at a temperature substantiallyequal to the saturation temperature corresponding to the pressure of thefluid within said tubes, and means for shielding a substantial portionof said one boundary wall from radiation within said furnace chamberincluding a shielding wall disposed on the gas side of said boundarywall and comprising a plurality of shielding tubes arranged inside-by-side relation, and means for passing a fluid through saidshielding tubes at a temperature above the saturation temperaturecorresponding to the pressure of the fluid within said shielding tubes.

4. In a high pressure fluid heating unit, upright boundary walls forminga heating chamber confining high temperature radiant heating gases, oneof said upright boundary walls including a plurality of parallelcontiguous vapor generating tubes rigidly united along their lengths. toform a rigid gas-tight wall panel, means for passing fluid.

in parallel flow relation through said tubes at a temperaturesubstantially equal to the saturation temperature corresponding to thepressure of the fluid'within saidl tubes, and means for shielding asubstantial portion of side of said boundary wall and comprising aplurality of spaced substantially parallel shielding tubes arranged withtheir longitudinal axes disposed at intersecting angles with respect tothe longitudinal axes of the tubes of said wall panel, and means forpassing a fluid through said shielding tubes at a temperature above thesaturation tempera ture corresponding to the pressure of the iluidwithin said shielding tubes.

5. In a high pressure fluid heating unit, upright boundary walls forminga heating chamber confining high temperature radiant heatin gases, oneof said upright boundary walls including a plurality of spaced parallelcontiguous vapor generating tubes, and metallic plate means rigidlyuniting said tubes along their lengths to form a rigid gas-tght wallpanel, means for passing fluid in parallel flow relation through saidtubes at a temperature substantially equal to the saturation temperaturecorresponding to the pressure of the fluid within said tubes, and meansfor shielding a substantial portion of said one boundary wall fromradiation within said furnace chamber including a shielding walldisposed on the gas side of said boundary Wall and comprising aplurality of spaced substantially parallel shielding tubes arranged withtheir longitudinal axes disposed at intersecting angles with respect tothe longitudinal axes of the tubes of said wall panel, and means forpassing a fluid through said shielding tubes at a temperature above thesaturation temperature corresponding to the pressure of the fluid withinsaid shielding tubes.

6. In a high pressure vapor generator, upright boundary walls forming afurnace chamber confining high temperature radiant heating gases. one ofsaid upright boundary walls including a plurality of spaced parallelcontiguous vapor generating and upright tubes, and metallic plate meansrigidly uniting said tubes along their lengths to form a rigid gas-tightwall panel, means for passing fluid in parallel flow relation throughsaid tubes at a temperature substantially equal to the saturationtemperature corresponding to the pressure of the fluid within saidtubes,

and means for shielding a substantial portion of said one boundary wallfrom radiation within said furnace chamber including a shielding walldisposed on the gas side of said boundary wall in spaced relationthereto and comprising a plurality of spaced parallel shielding tubesarranged with their longitudinal axes disposed at substantially rightangles with respect to the longitudinal axes of the tubes of said wallpanel, and means for passing a fluid through said shielding tubes at atemperature above the saturation temperature corresponding to thepressure of the fluid within said shielding tubes.

7. In a high pressure vapor generator, upright boundary Walls forming afurnace chamber confining high temperature radiant heating gases, one ofsaid upright boundary walls including a plurality of spaced parallelcontiguous vapor generating tubes, and metallic plate means rigidlyuniting said tubes along their lengths to form a rigid gastight wallpanel, means for passing fluid in parallel flow relation through saidtubes at a temperature substantially equal to the saturation temperaturecorresponding to the pressure of the fluid within said tubes, and meansfor shielding a substantial portion of said boundary wall from radiationwithin said furnace chamber including a shielding wall secured in spacedrelation to and supported by said boundary wall and disposed on the gasside thereof, said shielding wall comprising a plurality of spacedparallel shielding tubes arranged with their longitudinal axes disposedat substantially right angles with respect to the longitudinal axes ofthe tubes of said wall panel, the spaces betwewen said shielding tubesbeing less than the spaces between the tubes of the shielded portion ofthe boundary wall, and means for passing a fluid through said shieldingtubes at a temperature above the saturation temperature corresponding tothe pressure of the fluid within said shielding tubes.

8. In a high pressure forced-circulation vapor generator, uprightboundary Walls forming a furnace chamber confining high temperatureradiant heating gases, one of said upright boundary walls including aplurality of parallel contiguous and upright vapor generating tubesrigidly weld-united along their lengths to form a rigid gas-tight wallpanel, means for passing fluid in parallel flow relation through saidtubes at a temperature substantially equal to the saturation temperaturecorresponding to the pressure of the fluid within said tubes, and meansfor shielding a substantial portion of said one boundary wall fromradiation Within said furnace chamber including a shielding walldisposed on the gas side of said boundary wall in spaced relationthereto and comprising a plurality of spaced substantially parallelshielding tubes arranged with their longitudinal axes disposed atintersecting angles with respect to the longitudinal axes of the tubesof said wall panel, and means for passing a fluid through said shieldingtubes at a temperature above the saturation temperature corresponding tothe pressure of the fluid within said shielding tubes, the tubes of saidboundary wall and the shielding tubes being relatively serially arrangedfor the flow of fluid therethrough.

9. In a high pressure forced-circulation fluid heating unit havingupright boundary walls forming a furnace chamber confining hightemperature radiant heating gases, one of said upright boundary wallsincluding a supply header, a collection header, a plurality of spacedparallel contiguous and upright tubes connected for parallel fluid flowbetween the supply header and the collection header, an outlet headerdisposed adjacent said collection header, a plurality of U-shaped tubeseach having a pair of upwardly extending legs disposed in the plane ofsaid upright tubes, said Ushaped tubes being connected for parallelfiuid flow between the collection header and the outlet header, thefluid flowing through said upright tubes and said U-shaped tubes beingat a temperature no greater than the saturation temperaturecorresponding to the pressure of said fluid, and metallic plate meansrigidly interconnecting the adjacent portions of said upright tubes andsaid U-shaped tubes along their lengths to form a gas-tight wall panel,the legs of said U-shaped tubes extending over only the upper portion ofthe height of said wall panel, and means for shielding a differentportion of said wall panel from radiation within said furnace chamberincluding a shielding Wall disposed on the gas side of said boundarywall and in spaced relation thereto and comprising a plurality of spacedsubstantially parallel shielding tubes arranged with their longitudinalaxes disposed at intersecting angles with respect to the longitudinalaxes of the upright tubes of said wall panel, and means for passing afluid through said shielding tubes at a temperature above the saturationtemperature corresponding to the pressure of the fluid within saidshielding tubes.

10. A fluid heating unit as claimed in claim 9 wherein said uprighttubes and the legs of said U-shaped tubes are substantially the samediameter, the upright tubes are substantially straight in the plane ofthe boundary wall and are spaced on centers of about 4.5 times theirdiameter, the center of each leg of each U-shaped tube is spaced atabout 1.5 times its diameter from the center of its adjacent leg, andthe shielding tube centers are spaced less than 1.5 times theirdiameter.

11. The invention according to claim 7 wherein the shielding wall issecured to the Wall panel by plate members welded to the lateral centersof the metallic plate means at spaced locations across the width of thewall panel.

References Cited by the Examiner UNITED STATES PATENTS KENNETH W.SPRAGUE, Primary Examiner.

1. IN A FLUID HEATING UNIT, UPRIGHT BOUNDARY WALLS FORMING A HEATINGCHAMBER CONFINING HIGH TEMPERATURE RADIANT HEATING GASES, ONE OF SAIDUPRIGHT BOUNDARY WALLS INCLUDING A PLURALITY OF PARALLEL CONTIGUOUSVAPOR GENERATING TUBES RIGIDLY UNITED ALONG THEIR LENGTHS TO FORM ARIGID GAS-TIGHT WALL PANEL, MEANS FOR PASSING FLUID IN PARALLEL FLOWRELATION THROUGH SAID TUBES AT A TEMPERATURE SUBSTANTIALLY EQUAL TO THESATURATION TEMPERATURE CORRESPONDING TO THE PRESSURE OF THE FLUID WITHINSAID TUBES, AND MEANS FOR SHIELDING A SUBSTANTIAL PORTION OF SAID ONEBOUNDARY WALL FROM RADIATION WITHIN SAID FURNACE CHAMBER INCLUDING ASHIELDING WALL DISPOSED ON THE GAS SIDE OF SAID BOUNDARY WALL ANDCOMPRISING A PLURALITY OF SHIELDING TUBES ARRANGED IN SIDE-BY-SIDERELATION, AND MEANS FOR PASSING FLUID THROUGH SAID SHIELDING TUBES.